Large multi-ply corrugated paperboard containers are commonly used as bins for storing and transporting bulk materials. These containers are typically shipped to the users in a flat "knocked down" configuration to save space. In addition, these containers are used multiple times and are knocked down between each use. However, it is difficult to provide a multi-layer container that has the strength and stiffness to carry large quantities of bulk material and yet is easily knocked down without it having a tendency to spring back to a partially erected position. One way of accomplishing this is by providing beveled corners at two opposed corners or at all four corners of the container. These beveled corners are created by crushing the corrugated material. A container of this type is shown in Gillard U.S. Pat. No. 4,601,407.
These prior art containers are manufactured by wrapping a strip of single-ply corrugated material around a mandrel having beveled corners, with each layer being adhesively bonded to the underlying layer. A plate is urged inwardly against the corners to crush them. While containers made by this technique can be knocked down relatively easy, they still have a tendency to spring back and an expensive sophisticated mechanism is required to construct them.
The subject invention provides a method for manufacturing an easily knocked down multi-ply corrugated container, and the resulting container, which does not require specialized equipment. The method includes providing overlying inner and outer elongate, rectangular cross-sectioned, tubular corrugated shells with the walls of the inner shell being spaced apart from the walls of the outer shell, and corrugated panels which are located between and adhesively adhered to adjacent walls of the inner and outer shells. The panels preferably have a width which is less than the width of the walls leaving a space between the inner and outer walls at each corner. This space allows the container to easily be knocked down. In a preferred embodiment, the corners of the inner and outer shells are crushed to provide a wide break line which creates soft corners in the shells which further facilitates knocking the containers down.
Preferably, the inner and outer shells are made from two-ply, double wall corrugated material and the panels are made from one-ply, double wall corrugated material. Insertion of the panels between the shells so that they are centered on the walls is facilitated by inserting a spacer between each adjacent inner and outer wall at the sides thereof before inserting the panels.
The resulting container preferably is enclosed with a bottom cap having end flaps which project upwardly between any two adjacent plies. The outer shell has downwardly extending closure flaps which are foldable over this bottom cap. The bottom cap and closure flaps prevent the sidewalls of the container from bowing out and the closure flaps also prevent the bottom cap end flaps from being pulled out from between the adjacent plies when the pallet on which a loaded container is moved before the container has been strapped to the pallet.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.